Singlet−Triplet Energy Splitting and Excited States of Phenylnitrene

2008 ◽  
Vol 112 (37) ◽  
pp. 8649-8653 ◽  
Author(s):  
Michael Winkler
Keyword(s):  
Excited States ◽  
Energy Splitting ◽  
Triplet Energy

Controlling the exciton lifetime of blue thermally activated delayed fluorescence emitters using a heteroatom-containing pyridoindole donor moiety

2017 ◽  
Vol 4 (4) ◽  
pp. 619-624 ◽  
Author(s):  
Gyeong Heon Kim ◽  
Raju Lampande ◽  
Joon Beom Im ◽  
Jung Min Lee ◽  
Ju Young Lee ◽  
...  
Keyword(s):  
Molecular Design ◽  
Delayed Fluorescence ◽  
Energy Splitting ◽  
Triplet Energy ◽  
High Quantum Efficiency ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Exciton Lifetime ◽  
Low Efficiency ◽  
Donor Moiety

We demonstrate a promising molecular design approach to achieve short exciton lifetime, small singlet and triplet energy splitting and high photoluminescence quantum yield in thermally activated delayed fluorescence emitters for high quantum efficiency and low efficiency roll-off characteristics in OLEDs.

Forcing dimethylacridine crooking to improve the efficiency of orange-red thermally activated delayed fluorescent emitters

2020 ◽  
Vol 8 (30) ◽  
pp. 10416-10421
Author(s):  
Feng-Yan Hao ◽  
Yi-Zhong Shi ◽  
Kai Wang ◽  
Xiao-Chun Fan ◽  
Lin Wu ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Steric Hindrance ◽  
Fluorescence Quantum Yield ◽  
Energy Splitting ◽  
Triplet Energy ◽  
Thermally Activated ◽  
High Fluorescence ◽  
Planar Geometries ◽  
High Fluorescence Quantum Yield

By crooking conventional donor segments via suitable steric hindrance, nearly planar geometries, a small singlet–triplet energy splitting and a high fluorescence quantum yield can be realized simultaneously.

scholarly journals Manipulating spatial alignment of donor and acceptor in host-guest MOF for TADF

2021 ◽  
Author(s):  
Xiao-Ting Liu ◽  
Weijie Hua ◽  
Hong-Xiang Nie ◽  
Mingxing Chen ◽  
Ze Chang ◽  
...  
Keyword(s):  
Excited States ◽  
Delayed Fluorescence ◽  
Energy Splitting ◽  
Time Resolved ◽  
Face To Face ◽  
Spatial Alignment ◽  
Stacking Pattern ◽  
Donor And Acceptor ◽  
Loading Ratio ◽  
Triplet Excited States

Abstract Thermally activated delayed fluorescence (TADF) was achieved when electron-rich triphenylene (Tpl) donors (D) were confined to a cage-based porous MOF host (NKU-111) composed of electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (Tpt) acceptor (A) as the ligand. The spatially-separated D and A molecules in a face-to-face stacking pattern generated strong through-space charge transfer (CT) interactions with a small singlet-triplet excited states energy splitting (∼0.1 eV), which enabled TADF. The resulting Tpl@NKU-111 exhibited an uncommon enhanced emission intensity as the temperature increased. Extensive steady-state and time-resolved spectroscopic measurements and first-principles simulations revealed the chemical and electronic structure of this compound in both the ground and low-lying excited states. A double-channel (T1, T2) intersystem crossing mechanism with S1 was found and explained as single-directional CT from the degenerate HOMO-1/HOMO of the guest donor to the LUMO + 1 of one of the nearest acceptors. The rigid skeleton of the compound and effective through-space CT enhanced the photoluminescence quantum yield (PLQY). A maximum PLQY of 57.36% was achieved by optimizing the Tpl loading ratio in the host framework. These results indicate the potential of the MOFs for the targeted construction and optimization of TADF materials.

Studies on the Mechanism of the Photosensitized Dimerization of Pyrimidines

1972 ◽  
Vol 27 (5) ◽  
pp. 550-553 ◽  
Author(s):  
A. Kornhauser ◽  
M. A. Pathak
Keyword(s):  
Energy Transfer ◽  
Excited States ◽  
Carbonyl Compounds ◽  
Physical Mechanism ◽  
Uv Light ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Electron Donating Groups ◽  
Π State

Thymine-2-14C was irradiated with UV light (>300 nm) in water solutions in the presence of different sensitizers. Pyrimidines upon irradiation with wavelengths of 300—320 nm in the presence of some ketones as sensitizers, yield cyclobutyl pyrimidine dimers. The reaction occurs through a triplet-triplet energy transfer from the sensitizer to the substrate. The energy transfer, however, does not occur through a simple physical mechanism. The ability of a donor (e. g. ketone molecule) in its excited state to form a complex with the acceptor (pyrimidine molecule) appears to be a prerequisite in this type of photodimerization reaction. A correlation of the photochemical behavior of different ketones in this reaction with the nature of their excited states has been proposed. Carbonyl compounds possessing n, π* lowest triples are active in inducing pyrimidine dimerizations. By introducing some different electron donating groups to the ketone molecules that lower its π, π* state below its n, π* level, the sensitizing ability of the molecule appears to decrease or disappears completely. Ethylacetoacetate was found to be a more effective sensitizer than acetone or acetophenone. Likewise, dihydroxyacetone was found to be a potent photosensitizer in dimerization of thymine. Urocanic acid (UCA), a major UV absorbing compound in mammalian skin, did not show any sensitizing ability to induce cyclobutyl pyrimidine dimers on irradiation in the presence of thymine, with wavelengths greater than 300 nm.

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